alleryThe Lac Operon in E. coli is INDUCED (turned ON) by the presence of:
ALactose (which binds repressor and frees operator)
BGlucose (which inhibits the operon completely)
CGalactose only (the breakdown product)
DUV radiation (which damages the operator)
Answer & Solution
Correct answer: A. Lactose (which binds repressor and frees operator)
When lactose is present, it (as allolactose) binds the repressor protein, which falls off the operator.
Then RNA polymerase can transcribe the lacZ-Y-A genes.
Glucose has the opposite effect (catabolite repression).
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